Startling new theory about peopling of the Americas

A new study of DNA from Native American, New World and Asian populations suggests the first Americans did indeed come from Asia, but that their trip had one heck of a layover.

PLoS One

According to the new theory, from the University of Florida, people began gradually migrating from Asia and Siberia into Beringia — a landmass connecting Siberia to modern-day Alaska that wasn’t submerged by rising seas until 11,000 years ago — some 40,000 years ago. But at that time, 40 millennia ago, two major glaciers blocked their path southward.

So the newcomers stayed in a place that was habitable, if certainly not ideal. This population of about 1,000 to 5,000 people stayed in Beringia until the glaciers gave way, about 15,000 years ago, the Florida researchers say. They then spread into North America through Alaska or Canada.

From a summary of the study:

“This was the raw material, the original genetic source for all of the Americas,” said Michael Miyamoto, Ph.D., a professor and associate chairman of zoology in UF’s College of Liberal Arts and Sciences.

“You can think of the people as a distinct group blocked by glaciers to the east. They had already been west, and had no reason to go back. They had entered this waiting stage and for 20,000 years, generations were passing and genetic differences were accumulating. By looking at the kinds and frequencies of these mutations in modern populations, we can get an idea of when the mutations arose and how many people were around to carry them.”

Working with mitochondrial DNA — passed exclusively from mothers to their children — and nuclear DNA, which contains genes from both parents, UF scientists essentially added genetic information to what had been known about the archaeology, changes in climate and sea level, and geology of Beringia.

The result is a detailed scenario for the timing and scale of the initial migration to the Americas, more comparable to an exhaustive video picture rather than a single snapshot in time.

This study isn’t completely discordant with another recent study of the first Americans, which also found that the people came from a single, distinct Asian source. For a summary of the Clovis-First theory, which has long been thought to answer this question but is now being questioned by some archaeologists, see here.

It seems that, after decades of study, we might finally be getting close to answering the mystery of the first Americans.

15 Responses

“There is great debate as to when and how the ancestors of the Native Americans first came to the New World, which lice one day might help resolve. It is commonly thought that people traveling across land settled the Americas, but “they would have only had a tiny window of opportunity about 13,500 years ago when there was a gap in the ice sheets,” Reed said.

“However, we know that humans had made it deep into South America by 13,000 years, so it’s difficult to understand or impossible to believe they could have traveled all that in just a few hundred years,” he added. And DNA evidence “suggests people have been in the New World for 30,000 years, with some genes even suggesting 50,000.”

Another way people might have settled the Americas includes coming by sea, either hugging the coast in boats from northeast Asia or, perhaps improbably, crossing the ocean from the Pacific Islands. Future research with the lice could shed light on “when and by which route they came to the Americas, as well as the people with them.”

I find the concept of multiple waves of migration to be very satisfying, overall. . . .

” I think both are going to be true. People came here in multiple stages.”

I don’t think there’s much doubt about that, we just need time to gather more evidence.

What’s really interesting is the interplay between the hard evidence and the DNA evidence.

For example, I mentioned Thor Heyerdahl above to Myetel, because Heyerdahl’s expeditions clearly showed that ocean migration was possible in very ancient times by drift-sailing on the ocean current systems.

But Heyerdahl, who died in 2002, was also a pre-DNA explorer, and his data base was limited to the old-fashioned methods.

For example Heyerdahl:

” … found evidence that suggested that seagoing war canoes as large as Viking ships and lashed together two and two had brought Stone Age Northwest American Indians to Polynesia around A.D. 1100 ….

” The oral history of the people of Easter Island, at least as it was documented by Heyerdahl, is completely consistent with this theory, as is the archaeological record he examined (Heyerdahl 1958). …

” Genetic research has found, however, that modern-day Polynesians are more closely related to Southeast Asians than to American Indians.”

But again, it looks to me like ancient peoples were **really getting around**! :^D

Eric, your maps here show how dramatically changes in the earths temperature over time have affected the level of the seas. Speeding up the process of melting the ice as we are with the human induced buildup of CO2 will make the current map of the world obsolete much more quickly that would be the case without our influence.

Yes its the topic that will just not die and will have impacts we have not even yet figured out.

I like David’s comment “being pursued” why would they leave an otherwise safe environment, unless they were fleeing their father-in law with his daughter. But, the cruise on the Kon Tiki probably could not be compared to a Carnival Cruise for safety (maybe I should reserve that, after some of the expose I have seen of these cruises)